CODEWITHSUNDEEP
javaarraysjvm
yhware
yhware

Reputation: 532

setting two arrays equal to each other in java

I am writing a program that has a double array called data.

My code so far is the following.

public class DataSet {
private double[] data;
private int dataSize;

public DataSet(){
    dataSize = 0;
    data = new double [10];
}

public void add(double x){
    if(dataSize>= data.length){
        double[] newData = new double[data.length*2];
        System.arraycopy(data, 0, newData, 0, data.length);
        newData=data;
        newData[dataSize]=x;
        dataSize++;
    }
    else{
        data[dataSize] = x;
        dataSize++;
    }
}
}

as you can see I am adding new values to the array using the add method. However what I am unsure of is that when I do 

newData=data;

Can I just make this change to the next line?

data[DataSize] = x;

The reason why I am asking is whether the by setting the two arrays equal to each other, whenever I call data, I am in fact calling newData.

Upvotes: 1

Views: 10606

Answers (2)

Filipp Voronov
Filipp Voronov

Reputation: 4197

You've lost your created array (stored in newData) by assigning newData=data;

Replace

newData=data;
newData[dataSize]=x;

by

data = newData;
data[dataSize]=x;

Upvotes: 2

Peter Lawrey
Peter Lawrey

Reputation: 533500

You need to reassign data. There is also some tools in the JVM which help you.

public void add(double x) {
    if (dataSize >= data.length)
        data = Arrays.copyOf(data, data.length * 2);
    data[dataSize++] = x;
}

Upvotes: 5

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